This invention relates to an alignment method to irradiate an alignment light onto an alignment mark portion on a photo resist coated semiconductor substrate and to scan it, to therefore align to a photo mask, etc. on the basis of the resultant intensity of rays of reflected light of alignment light respectively reflected by the surface of the photo resist and the interface between the photo resist and the mark portion, and more particularly to an alignment method for the patterning used in the lithographic process for semiconductor devices.
In the manufacture of semiconductor devices, a photolithographic technique is used for forming various wiring, etc. In this lithographic technique, it is required to perform the alignment of a photo mask, etc. for patterning on the basis of positioning marks provided on the semiconductor substrate on which a photo resist is coated.
Conventionally, there are instances where photosensitive resin materials (photo resists) are used with dyes having a light absorption characteristic in the exposure wavelength, etc. being added thereinto with a view to suppressing a reflected light from the base substrate in the exposure process. Rather, resist materials having no light absorption property and excellent transparency are selectively used for the wavelength of an alignment light.
In the case of using such a photo resist, a distorted alignment waveform is likely to occur when a partially damaged mark is used.
This results in the problem that an alignment position obtained by processing such a distorted alignment waveform is apt to be shifted with respect to the true center of the mark, thereby deteriorating the detection reproducibility of the mark.